Radio signaling



Aug. 16, 1932. COHEN 1,872,246

RADIO SIGNALING Filed July 23. 1928 AmpZi/z er Jele for E w M 7 mi/2hr flefecfor r257 wa 2757" Patented Aug. 16, 1932 UNITED (STATE PATENT OFFICE Louis connn, or wnsnmeromnrs'mrcror oonumm name SIGNALING- Application. filed July 23, 1925. Serial No. 294,742.

(GRANTED UNDER m er orinaacnis, 1883, as AMENDEDVAI'ERIL s0, 192s'; 370 o. c.7572 4 The invention described hereininay' be manufactured and used by or for the Government for governmental purposes, without the payment to meof any royalty thereon.

This invention relates to the art of radio signaling and particularly to improvements in receiving systemsof radio signals.

Oneof the' objects of this invention is to provide. methods and means for the selective reception of radio signals; another object is to provide a method for the elimination of interfering signals of definite frequencies.

In the reception of radio signals much difliculty is experienced from' interferences caused by any transmitting stations which may happen to be located in the vicinity of the receiver. Even if the frequencies of the local transmitters arediiferent' from the fre quency of the signal to be received, the inter- 0 ferences may nevertheless be very serious if the frequencies of the interfering station'sare not widely different from the frequency of the received signal. In the case of broadcast reception it is practically impossible to 28 receive stations of frequencies which are close to the frequency of any local transmitting station which may be in operation, and that is true even for good 7 selective receivers. With a sharply tuned receiver it may be pos 36 sible to narrow the range of interfering frequencies, but whether the interference caused by a local transmitter covers a wide or narrow range of frequencies, the interference is there just the same and limits the useful as ness of the receiver; For a locality where several transmitting stations are operating on different frequencies it makes it impossible to' receive any distant station which may happen to be on a "frequency somewherewithin 40 the range of any of the frequencies of the local transmitters, and thus preventing the reception of many stations. y 7

It is the purpose of this invention to provide suitable methods and means for the elimination of interferences caused by local and thus preventing these interfering signals from acting on the receiver.

The principle embodied in this invention isfundamentally the same as that covered in my co-pending patent applications, Serial Number 233,919 filed'November' 17, 1927'and Serial Number 293,608 filed July 18, 1928 in which applications I have discussed a new method for selective tuning which consists in the use of a wave-conductor interposed between the antenna and the receiving'circuit system. In the latter of the above two referred to pending patent applications I have described a method for the reception of radio signals in which the antenna is connected to a wave conductor, the junction point of antenna and wave conductor is grounded through an impedance and a receivin system is coupled to the extreme open en of the wave conductor. I have pointed outthat' when thewaveconductor is adjusted toa quarter wave length or an odd multiple of quarter wave lengths of the signals to be received, the junction point of the'ant'enna and wave conductor is practically at 'zero potential for that particular signal and none of the signal energy is by-passed to ground through the impedance which is connected to thejunction point of antenna and wave con-j ductor. All of the sign'al'energy is absorbed by the wave conductor which isthen transmitted through electrostatic coupling to the receiving system. In this invention advan tags is taken of this principle to provide means for the elimination of interferences of stations of particular frequencies. The improvements contemplated in this invention will: appear'evident from the description and discussion of the accompanying drawing which showstypical embodiments of this invention. I

In the drawing:

Fig. 1 is a diagrammatic view of the em-' bodiment of the invention in which one wave conductor is associated in the proper manner with the antenna system; q,

' Fig. 2 is amodification showing the use of several wave conductors in association with' the antenna system. 1 Q

Fig. 3 is a modification of Fig. 1 showing a different method of adjusting the wave conductor.

Having particular reference to the drawing in which the same numbers designate similar parts; in l i 'ure l the'antenna l is connected through coupling coil 2 to ground 33; coupled to 0011 2 is a tuned circuit 4 consisting of secondary coupling coil 5 and variable condenser 6, suitable amplification and detecting means of the usual types are connected to the terminals 7 and 8. At the junction point 9 a wave conductor is connected-which consists of a solenoidal coil 10, ametal plate 11 in proximity-to the'coil, the metal plate being grounded at 3. The operation of the invention is as follows: The wave conductor 10, ll, 3 is suitably adjusted preferably to a quarter wave length or an odd multiple of quarter wave lengths of the interfering signal, the adjustment is effected by varying the distance separation of the coil 10 from the grounded metal plate ll, thereby varying the distributed capacity of the coil. w hen this adjustnient is made the junction point 9, in accordance with the theory discussed in the pending patent applications referred to' above, is at zero potential for that particular frequency and therefore no current flows in the coupling coil 2 and hence noeifect on the receiving circuit at. The wave conductor 10, ll, 3 absorbs all the energy of the signals of that particular frequency, rendering the receiving system free from any interference by the signals of that particular frequency. nor any other frequency, however, the wave conductor has very little effect, if any, and the receiving system responds in the usual manner. In this arrangement therefore it is possible to absorb completely the energy of an interfering signal of a particular frequency, and that without reducing appreciably the eliiciency of the receiving system for signals of other frequencies. 'i"his is amply borne out by experience and is in accordance with the mathematical deductions worked out by applicant.

Irrespective of theory, however, in practice it is simply a matter of the choice of a wave conductor of suitable design provided with means for adjusting this wave conductor to respond to the interfering signals and absorbing its energy, thereby realizing a condition of rendering the receiving system free from any disturbances which may otherwise be caused by these interfering signals;

The embodiment of the invention shown in Figure 2 differs from that of Figure l in that three separate wave conductors 10, ll; l0, 11'; 10', '11 are c-onnected to the junction point9. Each of these wave conductors is separately adjusted to a quarter wave length or' an odd multipleof quarter wave lengths of a different interfering signal, thereby preventing any of three diflerent interfe'ring signals of different frequencies for which these wave conductors are in adjustment to affect the receiving circuit.

This method may be extended for the elimination of interferences for any number of localtransmit'ting stations by the simple expedient of connecting on at 9 a number of wave conductors each separately adjusted to a frequency of eachofthe interfering signals. This system is of particular advantage for 10- calities where several broadcasting transmitters are in operation blanketing reception from different stations.

Figure 3 is a modification of Figure 1 showing a different method of adjusting the wave conductor. In this arrangement the wave conductorconsists of two coils 12 and 1 3connected in series at the ends 15 and 16 by the lead 14. Coil 13 is slidable within coil 12, and by sliding one c-oil Within the other an adjustment is effected. f

the ad- Other methods of accomplishing justmentof the wave conductor may be used than those shown in the foregoing description without departing from the spirit of the invention. a

I claim v r 1. I In a system for the reception of radio signals comprising an antenna, a coupling coil and ground connection constituting the antenna circuit, a secondary tuned circuit coupled to the said coupling coil, and suitable means for amplification and detection coupled to the said tuned circuit, an adjustable wave conductor connected at the junction point where the antenna is connected to the said coupling coil, said wave conductor being adj ustable to absorb the energyof an interfering signal of a particular frequency, the said wave conductorconsisting of a solenoidal coil placed in close proximity to a grounded metal plate, the adjustment being eifected by varying the distance separation of the said sole noidal coil from the said grounded metal plate.

2. In a system for the reception of radio signals comprising an antenna and a coupling coil and ground connection constituting the antenna circuit, a secondary jtuned circuit coupled with the said coupling coil, and suitable means for amplification and detection coupled to the said secondary tuned circuit, an adjustable wave conductor connected at the junction point where the antenna connects with'the said coupling coil, the said wave conductor being adjustable to a quarter wave length of the interfering signal which is desired to eliminate from the receiving system.

3. In a system for the reception of radio signals comprising an antenna and a coupling coil and ground connectionconstituting the antenna circuit, a. secondary tuned circuit coupled with the said coupling coil, and suitable means for' amplificationand detection coupledzto the said secondary tuned circuit,

an adjustable wa ve conductor connected at the junction point-where the antenna connects with the said coupling coil, the saidwave conductor being adjustable to an odd multiple of quarter wave lengths of the interfering signal which is desired to eliminate from the receiving system.

4. In a system for the reception of radio signals comprising an antenna, a coupling coil and ground connection constituting the antenna circuit, a secondary tuned circuit coupled to the said coupling coil, and suitable means for amplification and detection coupled to the said tuned circuit, a plurality of wave conductors connected at the junction point where the antenna is connected to the said coupling coil, each of the said wave conductors being adjustable to absorb the energy of some particular interfering signal, each of said wave conductors consisting of a solenoidal coil placed in proximity to a grounded metal plate, the adjustment of each wave conductor being separately effected by varying the separation distance of each of said solenoidal coils from each of the grounded metal plates associated therewith.

5. In a system for the reception of radio signals comprising an antenna, a coupling coil and ground connection constituting the antenna circuit, a secondary tuned circuit coupled to the said coupling coil, and suitable means for amplification and detection coupled to the said secondary tuned circuit, a plurality of wave conductors connected at the junction point where the antenna is connected to the said coupling coil, each of said wave conductors being separately adjustable to a quarter wave length of an interfering signal.

6. In a system for the reception of radio signals comprising an antenna, a coupling coil and ground connection constituting the antenna circuit, a secondary tuned circuit coupled to the said coupling coil, and suitable means for amplification and detection coupled to the said secondary tuned circuit, a plurality of wave conductors connected at the junction point where the antenna is connected to the said coupling coil, each of said wave conductors being separately adjustable to an odd multiple of quarter wave lengths of an interfering signal.

7. In a system for the reception of radio signals comprising an antenna, a coupling coil and ground connection constituting the antenna circuit, a secondary tuned circuit coupled to the said coupling coil, and suitable means for amplification and detection coupled to the said secondary tuned circuit, a plurality of wave conductors connected at the junction point where the antenna is connected to the said coupling coil, each of said wave conductors being separately adjustable to an odd multiple of quarter wave lengths of an interfering signal, each of said wave conductors comprising a solenoidal coil placed in close proximity to a grounded metal plate, the adjustment of each of said wave conductors being efi'ected by varying the separation distance of said solenoidal coil from the said metal plate. I

In testimony whereof I aflix my signature.

LOUIS COHEN. 

